The number of chocolates that Alice is losing per day is D1. Whereas, the number of chocolates that Bob is gaining per day is D2. Currently, the number of chocolates that Alice and Bob contains is A and B respectively.
You are required to calculate the number of chocolates that Alice has when Bob does not contain any chocolates.
Note
Input format
The first and only line contains four space-separated integers A, B, D1, and D2.
Output format
Print a single integer denoting the number of chocolates that Bob contains.
Note: It is guaranteed that the answer always exists.
Constraints
1≤A, B≤1031≤D1, D2≤1031≤D1≤A
Initially, Mr. A has 100 chocolates and Mr.B has 10 chocolates and it is given that Mr.A is losing 5 chocolates per day so it will take 20 days from today to become poor and in these 20 days Mr.B will gain 100*20 =2000 chocolates so Mr.B chocolates become 2010.